Lipoprotein, cholesterol and triglyceride metabolism will be studied in patients with genetically defined diseases affecting plasma lipoproteins to determine if these diseases are characterized by distinct pathophysiologic abnormalities. Findings regarding lipoprotein, cholesterol and/or triglyceride metabolism will be related to models of organ and cellular lipoprotein metabolism developed from in vivo experiments using human and animal organs and cultured cells. Patients with the following diseases will be studied: familial lypercholesterolemia, familial hypobetalipoproteinemia, abetalipoproteinemia, pseudohomozygous familial hypercholesterolemia, familial combined hyperlipidemia, familial type 3 hyperlipidemia, and familial hypertriglyceridemia. Information from these studies will help to formulate an integrated scheme of lipoprotein and lipid metabolism in the intact mammalian system.